Blast furnace construction

ABSTRACT

The invention relates to blast furnace linings containing refractory brick of the fireclay or high alumina types which between certain rows has disposed a layer of pitch impregnated ceramic fiber board to absorb thermal expansion of the brick and resist penetration of slags in the furnace.

United States Patent 1191 Wishon June 3, 1975 [54] LAST FURNACE CONSTRUCTION FOREIGN PATENTS OR APPLICATIONS Inventor: Berhl E. s Bethel Park, 938,363 10/1963 United Kingdom 266/43 [73] Assignee: Dresser Industries, Inc., Dallas, Tex.

Primary Examiner-Gerald A. Dost [22] Filed 1974 Attorney, Agent, or FirmRaymond T. Majesko [2]] Appl. No.: 435,550

[57] ABSTRACT if 8 2 The invention relates to blast furnace linings containb 4/ 5 re c y brick of the fi y or alumina [5 1 Md 0 Search 266/25 52/245 1 types which between certain rows has disposed a layer of pitch impregnated ceramic fiber board to absorb [56] Relerences cued thermal expansion of the brick and resist penetration UNITED STATES PATENTS of slags i the furnace.

2,047,227 7/1936 Robinson 266/43 3,6l6,108 10/1971 Whitehouse 266/43 x 6 Claims 2 Blast furnaces are tall, narrow shaft-like structures. They are charged with the iron-making raw materials at the top. Iron and slags are drawn from the lower part of the furnace. The hottest portion of the blast furnace is near the bottom. The blast furnace is lined with refractory brick. The bosh and lower inwall (side wall) are water cooled. At the top of the blast furnace. especially high temperatures are not encountered. Impact and abrasion are most severe in this zone. In addition. the lining must be able to withstand infrequent but sometimes rapid temperature change which can result from non-uniform furnace operation.

Since the advent of the carbon lined hearth and hearth side walls in blast furnaces, it is not uncommon for the furnace to run two normal campaigns on one carbon hearth. This improvement in the construction of the furnace has left the bosh and lower side wall area as the most vulnerable in the furnace. The bosh and lower side wall linings are continually washed by slags that are reactive with both acid and basic refractories. Slag attack is believed to be the primary mechanism of failure in this area of the lining. The up-grading of the conventional fireclay and high alumina refractories used in these areas has failed to provide sufficiently uniformly wearing linings to take full economic advantage of the hearths. The slags can penetrate the expansion joints in the linings before brick expansion completely seals the joint. Disruptive forces can thereby develop behind the hot face of the linings.

Mortars are commonly used in blast furnaces for the purpose of expansion allowance and by their rigid character and ceramic bond, show some resistance to acid slags. However, quite often their very nature does not allow sufficient expansion clearance for the high quality fireclay and high alumina brick used in lining the high performance blast furnace today.

Accordingly, it is an object of this invention to provide an improved refractory lining construction in the blast furnace bosh and lower inwall areas.

It is another object of the invention to provide a blast furnace lining that is resistant to slag attack and contains means for accommodating the thermal expansion of the brick in the refractory linings thereof.

In the drawings,

FIG. 1 is a schematic illustration of a portion of a blast furnace.

FIG. 2 is a blown-up section of a portion of the wall of the blast furnace illustrating the concept of the invention.

In accordance with the present invention, there is provided a blast furnace construction divided primarily into an upper inwall zone, a lower inwall zone, a bosh zone and a hearth zone. All of these zones have a refractory lining of the type necessary to satisfy the service requirements in that zone. In the high performance blast furnaces, the zones above mentioned are currently lined with a high quality superduty fireclay brick or a high alumina brick. Most of the hearth zone is lined with carbon brick. In the lower inwall zone and bosh zone which is subjected to the greatest slag attack, there are a plurality of rows of refractory brick and a layer of pitch impregnated ceramic fiber board sandwiched between a sufficient number of rows of these brick to absorb their thermal expansion and resist attack by slags.

2 The high quality fireclay and high alumina brick referred to in the preceding paragraph are well known to those skilled in the art. However. a typical composition for each type of brick is set forth below.

Fireclay Brick High Alumina Brick "US. Pat. No. 3.42l,9l7 US. Pat. No. 3,067,050

A commercially available ceramic fiber board can be employed in the present construction. Examples of these are Kaowool, a proprietary product of Babcock and Wilcox Company and Fiberfrax H, a proprietary product of Johns-Manville Company. The ceramic fiber boards are typically formed on insulating block manufacturing machinery from specially processed ceramic fibers and a combination of organic and inorganic binders. Kaowool block or board fibers have a typical chemical analysis of 52% SiO 42% Al O and minor amounts of impurities, such as TiO Fe O and MgO. This block would be characterized as a fireclay type block. A high alumina block would analyze more than 45% AI O The fiber boards are impregnated by conventional impregnation techniques, such as dipping and pressure vacuum. Pitches having a softening point between about l35F. and 2l5F. are easy to handle and impregnate the fiber block to the extent desirable. The fiber blocks can be baked after impregnation to reduce volatiles and set the pitch, also by well known techniques. The higher softening point pitches are preferred for best slag resistance.

Referring to the drawings, FIG. 1 illustrates a blast furnace 1 having an upper inwall zone, a lower inwall zone, a bosh zone and a hearth zone. FIG. 2 is a blownup section showing the construction of the wall 2 in the lower inwall zone 3 and bosh zone 4. The wall 2 contains a number of rows of refractory brick 5 divided at specified intervals with cooler plates 6. Between a specified number of rows of brick is disposed a layer of impregnated ceramic fiber board 7.-

In practice, about a V4 inch thickness of impregnated fiber board would be necessary for five courses of 3 inch thick brick lining or for every 15 inch of brick. However, construction experience would dictate the thickness necessary due to temperature and type of brick used. From a practical standpoint, a range of Va inch to inch thickness would be satisfactory. As the temperature increases in a given zone a larger thickness of block may be necessary. This could be accomplished by spacing the block between every third or fourth row instead of every fifth row, as opposed to using varied thicknesses of the fiber block. The opposite would be true for decreasing temperatures in a given zone.

Merely by way of example, a A inch thick Kaowool fiber board was impregnated with pitch having a softening point of [F. by conventional techniques. The impregnated board was mortared into a slotted high alumina brick of the above approximate chemical analysis to simulate a joint. The same thing was done with an unimpregnated fiber board of the same variety. 300

grams of slag were dripped on each sample in the slots at 2,700F. in a reducing atmosphere. The typical analysis of the slag sample was as follows:

Slag Analysis SiO A1203 TiO, Fe O CaO 4 MgO Alkalies The impregnated sample showed very little erosion by the slag while the unimpregnated sample showed almost complete slag erosion.

To check the thermal expansion under load, the tar impregnated /2 inch board referred to above was placed in a pier between two pieces of high alumina brick (same analysis as above). The pier was subjected to a vertical load of 25 p.s.i. while the temperature was increased from 100F. to l,000F. The results indicated that the impregnated fiber board would accommodate the brick expansion to the extent desired.

It is intended that the foregoing description be construed as illustrative and not in limitation of the invention.

Having thus described the invention in detail and with sufficient particularity as to enable those skilled in the art to practice it. what is desired to have protected by Letters Patent is set forth in the following claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. in a blast furnace construction having an upper inwall zone, a lower inwall zone, a bosh zone and a hearth zone, a refractory lining in at least the lower inwall and bosh zones consisting essentially of a plurality of rows of refractory brick and a layer of pitch impregnated ceramic fiber board sandwiched between a number of rows to absorb the thermal expansion of the brick and resist attack by slags.

2. Construction of claim 1 in which the layer of fiber board is between about /4: inch and inch thick.

3. Construction of claim 2 in which the layer of fiber board is sandwiched between about each 15 inch of brick thickness.

4. Construction of claim 1 in which the ceramic fiber board is composed of high alumina fibrous material.

5. Construction of claim 1 in which the ceramic fiber board is impregnated with a pitch having a softening point between about l35 and 215F.

6. Construction of claim 1 in which the refractory brick are selected from the group consisting of high alumina and fireclay brick. 

1. In a blast furnace construction having an upper inwall zone, a lower inwall zone, a bosh zone and a hearth zone, a refractory lining in at least the lower inwall and bosh zones consisting essentially of a plurality of rows of refractory brick and a layer of pitch impregnated ceramic fiber board sandwiched between a number of rows to absorb the thermal expansion of the brick and resist attack by slags.
 1. In a blast furnace construction having an upper inwall zone, a lower inwall zone, a bosh zone and a hearth zone, a refractory lining in at least the lower inwall and bosh zones consisting essentially of a plurality of rows of refractory brick and a layer of pitch impregnated ceramic fiber board sandwiched between a number of rows to absorb the thermal expansion of the brick and resist attack by slags.
 2. Construction of claim 1 in which the layer of fiber board is between about 1/8 inch and 3/8 inch thick.
 3. Construction of claim 2 in which the layer of fiber board is sandwiched between about each 15 inch of brick thickness.
 4. Construction of claim 1 in which the ceramic fiber board is composed of high alumina fibrous material.
 5. Construction of claim 1 in which the ceramic fiber board is impregnated with a pitch having a softening point between about 135* and 215*F. 